Various different propulsion principles exist today for accelerating projectiles through the barrel of a weapon system. The main division between these principles is based on whether projectile propulsion takes place by means of gas operation, electric operation or via a combination of these, at the same time as the propulsion principle(s) used in turn essentially determine which problems may arise in the different weapon systems.
Gas-operated weapon systems normally mean those systems which utilize the combustion gases which are formed after ignition of the propellant concerned for the shell, which propellant may now be liquid, solid or gaseous, although powder is still usually used. For example, in a conventional weapon, an ammunition round is fired by means of a firing device, normally a fuse, which ignites a propellent charge which, on combustion, develops a propellent gas quantity which is sufficiently powerful and expansive to accelerate the projectile rapidly out through the barrel of the weapon.
Electrically driven weapon systems instead utilize short electric pulses with high voltage and/or high current intensity in order to fire and propel the shell in ammunition adapted especially for electric operation.
In recent years, weapon systems based on combinations of both gas operation and electric operation, such as, for example, cannons which comprise either electrothermal propulsion or electrothermochemical propulsion, what are known as ETC cannons, have become increasingly important. In ETC cannons, use is made of, for example, electrical energy from a high-voltage source in order to bring about the actual ignition of the propellent charge, and then of on the one hand chemical energy from the combustion of this propellent charge and on the other hand electrical energy in the form of one or more pulses in order to supply more energy to the propellent gas in the form of plasma formation from the latter or via the creation of an electric potential difference along the barrel in order to increase the speed of the projectile.
In many hitherto known electrothermochemical weapon systems, the conventional fuse is replaced by a plasma generator. The plasma generator is filled with a preferably metal material which, via the electric pulses, is heated, vaporized and finally partly ionized, a plasma being produced, which, depending on the type of plasma generator, flows out through the front opening of the plasma generator or through a number of openings along its sides, what is known as a “piccolo”. The very high temperature (roughly 10,000° K) of the plasma influences the combustion of the propellant in several positive ways, which together result in a desired higher muzzle velocity of the projectile.
Rather briefly, it can be said that a typical modern ETC cannon consists of a cannon, the shell projectiles of which are essentially powder-gas-propelled, but where the shell is fired by means of electric ignition and its projectile is given an extra “push” via the plasma formation in connection with combustion of the propellent charge. However, there are also ETC cannons in which, after firing by means of a conventional fuse add “normal” combustion of the powder charge carried out subsequently, extra electrical energy is supplied to the projectile via the propellent gas further forward in the barrel by devices specially arranged there (see, for example, U.S. Pat. No. 5,546,844).
The technical problems which form the basis of the present invention are on the one hand the handling and storage problems which exist or can arise in the different weapon systems due to the weight, the moisture-sensitivity, the risk of electric short-circuiting etc. of the shell, and on the other hand the specific risk for ETC cannons that the cartridge case burns on in the barrel owing to electric short-circuiting between the cartridge case and the barrel. This is because the modern conventional cartridge case is manufactured from electrically conductive metal, usually brass. The burning-on is caused by the current and/or the voltage used during firing being intentionally or unintentionally conducted across to the cannon/artillery piece via the barrel. Moreover, the fact that the cannon/artillery piece becomes live constitutes an extra disadvantage for the gun crew.
It is therefore highly desirable to produce a new type of ammunition which is different from the abovementioned electrically conductive metal ammunition, has a considerably lower projectile weight than all comparable ammunition for conventional weapon systems and moreover is electrically insulated in order to prevent short-circuits and to minimize the risk of all or parts of the cartridge case burning on in the chamber or in the barrel.